Modern mobile phones, also referred to as cellular phones, have become widely used as a mode of communication for the general public throughout the world. One goal of mobile phone manufacturers has been to create a phone that can be easily carried on a person's body. Consequently, the design of mobile phones have constantly been improved upon to reduce the overall size and weight of the mobile phone. While these improvements have created a small, compact phone that can easily be carried on a person's body, they have also created acoustical problems that have detracted from the phone's audio functionality.
One of the largest problems incurred by users of mobile phones is the acoustic echo that occurs when users have a phone conversation. Modern cellular phones and some other types of telephone ‘handsets’ make a poor seal to a user's outer ear due to the small physical size of the handset's earpiece. Thus, when a conversation takes place on the phone, the speech signals received by the phone's receiver (referred to as the “receive speech”) leaks out of the adjacent ear cavity, about the ear pinna, into the room. Once the receive speech leaks out of the ear cavity (referred to as an “ear leak”), it will radiate through the air and reach the microphone input sound port(s) of the mobile phone, which then causes the far-end talker (the person on the other end of the line, also referred to as the far-end person) to hear a delayed, acoustic “echo” of their own speech. The pickup of this radiated echo by the mobile phone's microphone is called external acoustic coupling. This problem persists during the times the mobile phone is receiving speech, the so called “receive” state, and during the “doubletalk” state (when both user and the far-end talker simultaneously speak). As designers make mobile phones smaller, the microphone-to-ear distance becomes smaller and the microphone-to-user's mouth distance becomes greater. Both of these changes in distances have caused the echo pickup by the microphones to occur more frequently and severely. Accordingly, the echo heard by a far-end talker, via external acoustic coupling, has become the number one sound quality design problem in mobile phone designs.
Another problem incurred by users of mobile phones is the ambient/background noise that can reach the microphone input sound port(s) of the mobile phone and interfere with the ability of a far-end person to hear the user of the mobile phone when the user speaks. The smaller the mobile phone, the greater the distance becomes between a user's mouth and the microphone input sound port(s) of the phone. As this distance increases, more electronic amplification must be applied to the user's talking signal (referred to as “send” speech) because the speech level entering the sound port(s) is reduced. Unfortunately, this amplification subsequently raises the signal level associated with the ambient noise that enters the microphone port(s). Thus, in the send and idle (quiet) states, the dominant problem is the ambient noise that leaks into the microphone system and interferes with the far-end person's ability to listen to the speech of the user of the mobile phone.
Similar problems exist in other communication devices, including but not limited to, hands-free “speakerphones” that are used in automobiles and conference rooms. For example, in a hands-free speakerphone in a conference room, the receiving loudspeaker is typically positioned in close proximity to the microphone input sound ports of the phone. Thus, just as in a mobile phone, the receive speech will radiate through the air and reach the microphone input sound ports, which can cause the far-end talker to hear a delayed, acoustic echo of themselves. Further, the distance between a user's mouth and the microphone system of the speakerphone is great and electric amplification of the send speech is required. Thus, similar to the mobile phone, a speakerphone requires amplification of the send speech, which in turn amplifies the ambient noise picked up by the microphone system. This amplification of the ambient noise interferes with the far-end person's ability to listen to the user of the speakerphone.
Accordingly, it is desired to provide a microphone system for communication devices that greatly reduces the external acoustic coupling of any type of communication device. Further, it is desired to provide a microphone system for communication devices that attenuates the pickup of ambient noise by the microphone system while still being sensitive to the user's speech.